Herbicidal effectiveness of trifluralin as influenced by methods of incorporation into the soil and depth of weed seed germination PublicDeposited

Descriptions

This study was conducted to compare the effectiveness of four
methods of incorporating the herbicide trifluralin into the soil, and
to determine the interaction between depth of incorporation of trifluralin
and depth of weed seed germination.
Field experiments on green and dry peas were established in
Oregon and Idaho. Trifluralin, applied at four rates, was incorporated
by a rototiller, tine-tooth harrow, spike-tooth harrow or
double-disked, prior to planting. At time of harvest, yields were
taken and plots were evaluated for weed control. On dry peas, only
the tine-tooth harrow gave unsatisfactory incorporation of trifluralin.
Increasing the rate of trifluralin, regardless of the method of incorporation,
reduced the yield of dry peas, indicating injury. On
green peas, both the double-disk and rototiller satisfactorily
incorporated trifluralin. However, yields from the rototiller plots
were slightly less than those from the disk plots. No injury was
noted with increasing rates of trifluralin.
Greenhouse experiments were conducted at Corvallis to determine
the effect of increasing the depth of incorporation and depth of
weed seed germination on the herbicidal activity of trifluralin. Trifluralin,
applied at three rates, was incorporated to four depths and
planted at three depths to pigweed (Amaranthus retroflexus L.) and
barnyardgrass (Echinochloa crusgalli (L.) Beauv.). Pigweed was
not affected when planted below the trifluralin-treated zone. Only
pigweed plants whose roots grew into the trifluralin were controlled.
Shoot uptake appeared to be more effective than root uptake by barn-yardgrass. When trifluralin was incorporated over 1.5 inches,
weed control was reduced, indicating a dilution effect.
Results of this study indicate that the weed species to be controlled
will be of major importance when determining the depth and
method of incorporation of trifluralin.